Author: markj Date: Mon Sep 16 15:16:48 2019 New Revision: 352411 URL: https://svnweb.freebsd.org/changeset/base/352411
Log: Assert that the refcount value is not VPRC_BLOCKED in vm_page_drop(). VPRC_BLOCKED is a refcount flag used to indicate that a thread is tearing down mappings of a page. When set, it causes attempts to wire a page via a pmap lookup to fail. It should never represent the last reference to a page, so assert this. Suggested by: kib Reviewed by: alc, kib Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D21639 Modified: head/sys/vm/vm_page.h Modified: head/sys/vm/vm_page.h ============================================================================== --- head/sys/vm/vm_page.h Mon Sep 16 15:12:49 2019 (r352410) +++ head/sys/vm/vm_page.h Mon Sep 16 15:16:48 2019 (r352411) @@ -902,13 +902,17 @@ vm_page_in_laundry(vm_page_t m) static inline u_int vm_page_drop(vm_page_t m, u_int val) { + u_int old; /* * Synchronize with vm_page_free_prep(): ensure that all updates to the * page structure are visible before it is freed. */ atomic_thread_fence_rel(); - return (atomic_fetchadd_int(&m->ref_count, -val)); + old = atomic_fetchadd_int(&m->ref_count, -val); + KASSERT(old != VPRC_BLOCKED, + ("vm_page_drop: page %p has an invalid refcount value", m)); + return (old); } /* _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
